Photo-electric cell



T. w. CASE.- PHOIO-ELECTRIC CELL. APPLICATION rim) AUG-27.1920.

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. THEODORE CASE, OF SCIPIO, NEW YORK.

PHOTO-ELECTRIC CELL.

Specification of Letters Patent.

Application. filed August 27, 1920. Serial No. 406,464.

To all whomit may concern:

Be. it known that I, THEODORE W. CASE, of Scipio, in the county of Cayuga in the State of New York have invented new and useful Improvements in Photo-Electric Cells, of which the following, taken in connection with the accompanying drawings, is

a full,- clear, and exact description.

This invention relates to certain improvements in photo-electric cells.

The object of the invention is to produce a highly efficient cell of the character described, and which shall be of simple construction, unusually constant and uniform in reaction, and relatively permanent in its activity.

Other objects and advantages relate to the details of construction of the cell, all of which will more fully appear from the following description, taken in connection with the accompanying drawings, in WhiClflt- Figure 1 is a diagrammatic view illustrating a method of carrying out one step of the process of producing the cell.

Fig. 2 is a diagrammatic view illustrating a manner of use of the cell of this invention.

The completed cell of this invention consists of a vacuum tube inclosing a plurality of electrodes one of which is provided wit 2 a coating of strontium deposited thereon in a manner tobe hereinafter described.

The invention, however, contemplates and permits 01? the introduction of a quantity of an inert gas, such as argon or helium, intd the vacuum tube containing the electrode.

.Under such circumstances, it may be suggested that the photo-electrons emitted by the action of light ionize the inert gas by impact ,resultingin maximum conductivity.

It is believed at present that the constant and uniform re-action of the cell, its relative permanency of activity and great intensity are largely the-result of the peculiar structural form of oneof the electrodes of the. cell -due to the peculiar and novel method of manufacture. 1-.

The physical structure of the coating of metaldeposi'ted uponone of the electrodes is known with absolute oertainty, and the theory of the action that results in the unexpected sensitivity of the element so produced is more or. less a matter for intelligent speculation, and the ap licant hesitates to state positively any definite theory, and desires to confine himself to the demonstrated fact that the element highly sensitive and relan in its activity, but with this so produced is tively permanent reservation it may be suggested as indicative of applicants present theory, that the metal deposited in the form of a coating upon one of the electrodes is in a peculiar structural condition resultant from the fact of its deposit in the manner to be described under constant bombardment by cathode rays or electrons.

The rocess of manufacture described and claime in my co-pending application, Serial No. 406,462 comprises primarily the coating of an electrode capable of being heated, such as a filament with strontium oxid. This coating may be produced upon the filament in any suitable way, as by dipping the same in strontiumnitrate at a suitable temperature to cause the same to flow upon the filament, and, by increase in temperature, change the nitrate to an oxid.

The coated filament is then placed in an ordinary glass tube or bulb opposite a metallic e ectrode, as for instance a nickel plate. The bulb is then evacuated and the whole'is baked at such a temperature as may be suitable for eliminating practically all traces of gases. Then the filament an metallic electrode are preferably connected in a circuit with a source of sufiiciently high Patented May 3, 1921.

potential so as toheat the metallic'electrode e electrode temperature is then reduced by regulating the potential to that found by experiment most suitable under the circumstances for the particular operating conditions without heating the electrode to a red heat. Asuitable circuit is provided containing a source of potential for heating the filament to such a temperature as will result in throwing oif the said filament coating in the form of relatively small particles.

By connecting the filament and metallic electrode in a circuit containing a suitable source of potential of the coating applied to the filament is, .to a very large extent, caused to be deposited upon the metallic electrode. In. other words, the high'potential existing between the electrodes acts as a directive agency and causes the thrown-01f material to deposit upon the metallic electrode'in a thin layer, where it is continuously bombarded by the cathode the thrown-ofi material rays, or electrons, emanating from the filament and directed bythe potential-of the metallic electrode. -It is believed that when a filament, as described, is coated with strontium oxid, that the oxid is lost when the material is finally deposited on the metallic electrode, and that the deposit upon the metallic electrode is a coating of substantially pure strontium.

Although a high potential direct current is suitable-for the purpose described, the applicant in his work has usually incorporated a transformer in the circuit whereby the potential of the alternating current available was stieipped up to an extent suitable for most e ctively acting as a directive agency of the material thrown off from the fila- I stated intervals, as, for instance, five minute periods, and after each such period the photo-electric qualities of the cell may be tested in comparison with-a constant source of li ht, and when the maximum reaction is obta ned, the vacuum pump ma be shut ofi and. the tube contaimng the ament and metallic electrode sealed.

During the process of manufacture, when using a direct current, the potential in the circuit is so arranged as to maintain a pos1- tive potential upon the metallic electrode and a negative potential upon the filament.

In Fig. 1, I have diagrammatically illustrated a hook-up suitable for car g out the depositing step of this process in which the'filament -1-- is connected in an independent heating circuit 2- with a source of potential '-3 andin which the cir "'t between thefilament 1 andmetallicv e ectrodes -2 includes the secondary 4- of a transformer, the primary 8 of which is connected in circuit with a suitable source of alternating current. The second a a of the transformer embodies a'considerab y larger number ofcoils than the primary'to produce desired voltage. When the process (gmproducing the cell is completed as descri the filament is thereafter u only as an unheated electrode, and any other Q form of, electrode maybe substituted;

In Fig. 2 I have illustrated the cell in a hook-up suitable for measuring light 1ntensity in which two electrodes are connected in circuit with a source of potential --7- and a galvanomet'er -5-. Variations in' the light rays to which the cell (which includes the electrodes --1 and -2 and the vacuum tube or bulb is exposed,

will be accurately indicated in a known 1 standard of measurement by the galvanometer 5.

The process above described permits of practically perfect control in the manufacture of cells of uniform action. Further, i

the method offers a substantially perfect control in obtaining the desired spectral sensitivityof the cell b combinin the proper substances on the filament to deposited on the metallic electrode, and by permitting control of the deposition by proper potential between the electrodes and proper temrature. What I claim is:

' 1. A photo-electric cell including an electrode having a coating of strontium.

2. A photo-electric cell including an'electrode comprising strontium.

3. A photolectric cell including an 510etrode having) a thin .ooating comprising' strontium. r

4. Aphoto-electriccell includingfan electrode having a-coating of strontiumdeppsifl. ed under bombardment; by cathode rays,

5. A photo-electric'cell 1ncluding an elec trode comprising strontium deposited under bombardment by cathode rays.

6. A photo-electric cell including an electrode having a thin coating comprisingstrontium deposited. under bombardment by cathode rays. v v.

7. A photo-electric cell includingan electrode having a coating of flight re-activ'e material deposited in ate-medians, particles upon said-electrode. i g I i 8 A photo-electric cell including-"an etrode'having acoatin of light re-active ma- .terial deposited, 'un er electron bombardmerit, in the form of fine particle'ss upon said electroda p I i In Wi s hereof I have hereunto gal;

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